Zircon compatible, ion exchangeable glass with high damage resistance

Abstract

An ion exchangeable glass having a high degree of resistance to damage caused by abrasion, scratching, indentation, and the like. The glass comprises alumina, B 2 O 3 , and alkali metal oxides, and contains boron cations having three-fold coordination. The glass, when ion exchanged, has a Vickers crack initiation threshold of at least 10 kilogram force (kgf).

What is claimed is: 
     
       1. An article, comprising:
 a layer extending from a surface of the article to a depth of layer, wherein the layer is under compression; 
 wherein the article is formed by ion exchanging a glass, wherein the glass comprises:
 66-74 mol % SiO 2 ; 
 9-20 mol % Na 2 O; 
 9-22 mol % Al 2 O 3 ; 
 at least 2.7 mol % B 2 O 3 ; 
 at least 0.1 mol % of at least one of MgO and ZnO, 
 wherein R 2 O (mol %)+CaO (mol %)+SrO(mol %)+BaO(mol %)−Al 2 O 3  (mol %) −B 2 O 3  (mol %)<0 mol %. 
 
 
     
     
       2. The article of  claim 1 , wherein the glass has a zirconia breakdown temperature that is equal to the temperature at which the glass has a viscosity in a range from 30 kPoise to 40 kPoise. 
     
     
       3. The article of  claim 1 , wherein the glass comprises:
 from 10 mol % to 20 mol % Na 2 O; 
 from 0 mol % to 5 mol % K 2 O; 
 0.1 mol % ≤MgO≤6 mol %; 
 0 mol % ≤ZnO≤6 mol %; and 
 0 mol % ≤CaO(mol %)+SrO(mol %)+BaO (mol %)≤2 mol %. 
 
     
     
       4. The article of  claim 1 , wherein B 2 O 3  (mol %)−(R 2 O (mol %)−Al 2 O 3 (mol %))≤4.5 mol %. 
     
     
       5. The article of  claim 1 , wherein the glass comprises at least 10 mol % R 2 O. 
     
     
       6. The article of  claim 1 , wherein the glass is substantially free of Li 2 O. 
     
     
       7. The article of  claim 1 , wherein the glass is characterized by B 2 O 3 (mol %)−(R 2 O(mol %)−Al 2 O 3  (mol %))≥3 mol %. 
     
     
       8. The article of  claim 1 , wherein the glass is characterized by 3 mol % ≤B 2 O 3 (mol %)−(R 2 O(mol %)−Al 2 O 3 (mol %))≤4.5 mol %. 
     
     
       9. The article of  claim 1 , wherein the glass comprises 3-4.5 mol % B 2 O 3 . 
     
     
       10. The article of  claim 1 , wherein the glass comprises 2.7-4.5 mol % B 2 O 3 . 
     
     
       11. The article of  claim 1 , wherein the glass comprises 3-10 mol % B 2 O 3 . 
     
     
       12. The article of  claim 1 , wherein the glass comprises at least 0.1 mol % MgO. 
     
     
       13. The article of  claim 1 , wherein the layer comprises a compressive stress of at least 600 MPa. 
     
     
       14. The glass of  claim 13 , wherein the compressive stress is at least 800 MPa. 
     
     
       15. The article of  claim 1 , wherein the depth of layer is at least 30 μm. 
     
     
       16. The article of  claim 1 , wherein the article has a Vickers crack initiation threshold of at least 10 kgf. 
     
     
       17. The article of  claim 1 , wherein the article has a Vickers crack initiation threshold in a range from 20 kgf to 30 kgf. 
     
     
       18. The article of  claim 1 , wherein the article has a Vickers crack initiation threshold in a range from 30 kgf to 35 kgf. 
     
     
       19. A device, comprising at least one of:
 a cover plate; 
 a touch screen; and 
 a screen, wherein the cover plate, the touch screen, or the screen comprises the article of  claim 1 . 
 
     
     
       20. A watch crystal comprising the article of  claim 1 .